JPS5895452A - Controlling system for demodulation carrier phase - Google Patents

Abstract

PURPOSE:To correct the group delay distortion in a demodulating circuit, by controlling a demodulation carrier by a phase error, which is obtained from the difference between a demodulated impulse response and a reference level, in the demodulation of the transmission system using the class IV (10-1) partial response encoding. CONSTITUTION:A demodulation signal which is obtained from an input terminal and is converted to a class IV partial response code is sent to a pattern detector 1, which detect pattern (+ or -1, 0, + or -1), and an error detector 2 which operates the difference between the demodulation signal and a reference level signal 12 to detect the polarity of phase error information as an error signal. A storing equipment 3 stores this error signal, and the error signal is sent to an integrator 4 only when a signal is outputted from the pattern detector 1. The phase of the demodulation carrier is controlled by a control voltage 13 from the integrator 4. Thus, the waveform distortion due to the group delay distortion of a transmission line is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to class I V ternary
This invention relates to a demodulation carrier phase control system for a received pace signal encoded by a digital signal.

Generally, in waveform transmission of data signals, etc., the demodulated signal (hereinafter referred to as received signal) is determined by the phase of the demodulated carrier.
It is well known that the waveform of a signal changes, but if amplitude distortion or group delay distortion does not occur in the transmission path, it is possible to demodulate a signal without waveform distortion by so-called synchronous detection (demodulation). . On the other hand, if there is distortion in the transmission path, especially if there is group delay distortion, if the phase of the demodulated carrier is given without any restrictions, such as during the synchronous detection, the waveform will change with respect to the received signal. Distortion occurs and the transmitted data cannot be reproduced accurately. Therefore, conventionally, the waveform distortion of the received signal can be reduced by manually adjusting the phase of the demodulated carrier appropriately, but this must be readjusted every time the characteristics change due to switching of the transmission path, etc. There was a drawback.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to correct and demodulate the received signal, which is received with waveform distortion on the transmission line, without distortion, to the output side of the demodulator, even if the transmission line is switched or the characteristics change. The object of the present invention is to provide a demodulation carrier phase control system with a simple configuration.

According to the present invention, in a waveform transmission method using a data signal in which a modulated and transmitted Class I ■ ternary partial response encoded tatator signal is received and demodulated via a transmission path, (+1, 0) of a received signal.

-1) or (-1, 0, +1); an error detector that detects an error between the received signal and the reference level signal; , 0 , -1 ) or (-1
, 0, +1), the stored error signal is integrated and smoothed by the integrator, and when the polarity is positive, retards the phase (for lower sideband modulation), advances (for upper sideband modulation), advances the phase of the demodulated carrier (for lower sideband modulation) if the polarity is negative, (In the case of upper sideband modulation) A demodulation carrier phase control method characterized by performing delay control is obtained.

Next, an embodiment of the demodulation carrier phase control method according to the present invention will be described with reference to the drawings.

Figure 1 shows the impulse response when synchronous detection is performed on a class IVa value partial response encoded data signal with no distortion in the transmission path. Figure 2 shows the impulse response when synchronous detection is performed without adjusting the phase of the demodulated carrier in a state where group delay distortion occurs, and the slope opposite to the above (temporarily referred to as negative slope) in the transmission path. FIG. 3 shows an impulse response when synchronous detection is performed without adjusting the phase of the demodulated carrier in a state where group delay distortion of . However, in these figures, assuming that the transmitter system is limited by the bandwidth B, the period T is T = 1/2
If we shift the phase of the demodulated carrier from the transmission line distortion-free, synchronous detection state shown in Figure 1, which is expressed as The impulse response is as follows. Therefore, when the group delay distortion has a positive slope, there is an optimal demodulated carrier phase that can be approximated to the impulse response shown in Figure 1 by delaying the phase of the demodulated carrier; In the case of a transmission line having a group delay distortion of , as the phase of the demodulated carrier is advanced, there exists an optimum phase that can similarly approach the impulse response shown in FIG. 1.

FIG. 4 is an operational waveform diagram of the present invention, where a in FIG. 4 is the impulse response in FIG. 3, b is the reference voltage of the impulse response C in FIG. 1, and d is phase error information. .

In Fig. 4, the impulse response of a is brought close to the impulse response of shea a by integrating and smoothing the phase error information of d, and the impulse response is corrected to the best condition. What is necessary is to stop the phase adjustment.

Also, in the case of the impulse response shown in FIG. 2, the operation is the same except that the direction of phase correction is opposite to that described above.

Next, an embodiment of the present invention will be described with reference to FIG. Input terminal 1
The class IVa value partial response encoded received signal supplied from 1 is provided with a 3-bit shift register, (+1, O, -1), (-1°0, +1
), and an error detector that detects the polarity of the multiphase error information as a vt difference signal by taking the difference between the received signal and the reference level signal 12. Memory @3 stores this error signal, and the pattern detector 2 detects (+1, O, -1) or (-1,
0, +1) is detected, the stored error signal is sent to the private divider 4, and is integrated and smoothed by the integrator 4, and the control voltage 13 obtained is used to detect the demodulated carrier if the polarity is positive. Waveform distortion of the received signal caused by group delay distortion of the transmission path can be corrected by delaying the phase so that the 'ff1E carrier has the optimal phase and advancing the phase so that the 'ff1E carrier has the optimal phase if the polarity is negative. be done.

As is clear from the above description, according to the present invention,
Without the need for expensive correction functions like automatic fixtures,
With a simple circuit configuration, the waveform distortion of the received signal caused by the group delay distortion of the transmission line can be automatically corrected by adapting to variations in the characteristics of the transmission line. A great effect can also be obtained in improving the quality of the food.

[Brief explanation of drawings]

Garbage is 1, food is 2, and cutting is 3. General class IVa.
Waveform 1 shows the synchronized detection ratio of the data signal of value partial response + f-Q conversion, Figure 4 is a waveform diagram for expanding the principle of the present invention, and Figure 5v1 shows the main part of the embodiment of the present invention. It is a block diagram. 1... Pattern detector, 2... Differential/output device, 3... Memory Hi 1.4... Wa 1
Divider, 11...Input terminal, 12...Base level signal, 13...Control voltage. Number l Zute 2 Zuken 3 Sono

Claims (1)

[Claims] From the received signal encoded with class IVB value partial response (+1, 0-, -1), (-1, O,
a pattern detector that detects the pattern of (+1); an error detector that obtains an error signal indicating the polarity of the phase difference between the received signal and the reference level signal; and an error detector that stores the error signal and detects the pattern of (+1). .0.-1). A memory device outputs the error signal stored only when a pattern of (-1, 0, +1) is detected, and the output of the memory device is integrated and smoothed, and if the polarity is positive, the phase of the demodulated carrier is changed. Delays for lower sideband modulation, advances for upper sideband modulation, and advances the phase of the demodulated carrier if the polarity is negative for lower sideband modulation and retards for upper sideband modulation A demodulation carrier phase control method characterized by comprising an integrator that outputs a control signal for controlling.